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Discussion Starter #1 (Edited)
I was out at VIR North track the past few weekends and rode both my 1098 Ducati and my GSX-R600 Suzuki. There is a very pronounced difference in the force on the bars required to turn the two bikes as the speed gets up in the 120 to 150 range past the kink at the oak tree on the front straight. I have to shove on the bars with a much greater force on the 1098 than on the Suzuki and I have been wondering why the big difference.
The 1098 has the Dan Kyle 30mm triple clamps and a ride height of 6.5 eye to eye on the height adjuster. The bike is wonderful over all and I have no complaint with it. The suspension is dialed in perfect for me making the bike feel like it is on rails and corners like magic. It is a bit heavier so I do have to use some mussel to change directions but not overly so in the slower sections.
The Suzuki set up is basically stock with the rear spring being replaced for my wieght.
The Suzuki feels great no matter where it is or how fast it is going.
The Ducati has Pirelli slicks same as the Suzuki with the Suzuki running a 180-55 VS the 190-55 on the Ducati. Both bikes run the same Pirelli front tire.
Both bikes have been adjusted and tweeked for me by Dave Moss out of California.
The Suzuki runs a 24 degree rake stock and the 1098 runs a 24.5.
The Ducati retains the stock wheels as does the Suzuki.
Question is why the big difference in force required to turn the two different bikes at speed?
Rotating mass is different I am sure between the two bikes but is it enough to show up this way?
 

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I think the main difference is the overall weight. While both bikes are light for their respective classes, the Suzuki is still way lighter than the 1098.
Almost anytime you try to change direction on an object that is heavier, it will take more force to do so.

By the way, I commend you on your suspension set-ups. Very nice!
 

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I rode my nephew's 600 GSXR back from San Marcos for him last weekend. There is a marked difference in the steering of the GSXR and the 748; the 748 seems to hold a more solid line, requiring more force to hold it, while the GSXR seems to be more responsive to the pressure but needed more "adjustment" during the curve.

Could tightness of the steering neck bearing make a difference?
 

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There was a formula floating around about a year or so ago which indicated the amount of force required to change direction of a rotating front wheel due to rotational inertia. For every bit of weight you reduced on the wheel resulted in a reduction of X kilograms of force required to change direction at Y speed.

Even if there is only a 1 kg difference in front wheel weight, then there will be a marked difference in force required to change direction. Ask any guy who has put BST wheels on his bike if he will ever put the stock rims back on again.... the answer 99% of the time will be no because it is so much easier to steer a BST wheel through a corner.

Now add the differences of rotational inertia between the two bikes from the smaller clutch, lighter fly wheel, lighter crank etc and it all adds up to easier directional changes. Just look at the difference between the 749 and the 999


SF
 

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Discussion Starter #5 (Edited)
The Ducati is set up with roller bearings vs the stock ball bearings but the feel is just as light as the stock set up. The steering head is adjusted perfect, not too tight and just a skinny bit tighter than loose play.
The old Newtonian laws, dang. An object in motion tends to stay in motion or on its trajectory until acted upon by another object or force.
The .5 degree rake difference is a factor I suppose as well.
I was watching the World Superbike Races this evening and one of the commentators said the "Ducati was a little harder to turn in than the in line fours" for what ever that is worth.
I did try to raise the rear ride height from the now 6.50 to 6.56 a 1/16th inch increase and did not like it, can't remember what the actual ride height difference was using a ride height tool but I think it was about 1/4 inch increase.

General set up information on my 1098 base model:
Ohlins DU515 shock, 6.5 eye to eye ride height.
20mm Ohlins Fork kit installed in the stock Showa forks by Rick at Cogent Dynamics with .95 springs and 2 lines showing on the fork tubes not counting the fork cap using Dan Kyles 30 mm off set triple clamps. Preload is six lines showing + two turns out, love it. I don't know what weight oil or how much Rick put in but the 2008 unit will be next and I will ask just so I know in the future.
Settings and rear spring details are written down out in the trailer if anyone wants them I can get them in the morning. I weigh in at 200 with gear.
I removed the radiator fans and moved the bottom of the radiator back about 3/8ths of an inch using a flat piece of aluminum as a link. The radiator will not go back that far with the fans still installed. I was touching the bottom of the radiator with the front tire before I moved it. The bike is track only so no worry about sitting in traffic, temp runs in the 168 degrees F area when moving.

Like I said I have no real complaints with the 1098 just wondered about the turning thing.
I have been using Pirelli slicks this summer and love them. Some like Dunlops some like something else but I figure if I stick with what works for me I will be ahead of the game. I tried the Power One commercial tires on the Suzuki but found their edge and then went with the Pirellis on it as well.
Thanks for helping me figure this out.
Safetyfish;
I forgot about all the other stuff whirring around, great point!!
Hey, is that dog for real?? H^&* Cr$p!!!
 

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Could tightness of the steering neck bearing make a difference?
Probably not. When the bikes are up on stands, the steering moves easily on both bikes.

I have both a 1098 and a GSXR-600 too, and they handle night-and-day differently. The GSXR does in fact turn in with about half the force required on the 1098. And you're right, it does seem to require more correction all the time, while the 1098 is more solid and steady through the turns. Thats at normal everyday speeds. At supra-legal speeds above 100mph, the 1098 is the one that turns in faster.

I know the GSXR's wheels definitely have more mass than the Marchesini's on the 1098.

My thought is rake difference, or possible the difference in where the clip-ons are mounted and the leverage you get. If not that, then possibly wheelbase or the rotational forces of the engines are at play.

I have no idea, but I definitely know the differences you're talking about with those two bikes.
 

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Another possible explanation is the difference in location of the center of gravity and wheel base of both bikes. The Suzuki is at least in inch shorter in wheelbase, and the CG is likely higher and forward than that of the 1098. Both contributing factors to easier turn-in.
 

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I´m also guessing that the 30mm offset triples have some impact here.
Reducing trail makes the bike harder to turn in, but the bike will hold and exit a turn better/tighter.

I´ve heard of afew people running the rear excentric at the 3 O´clock rear position tom combat this behavior since it reduces trail without shortening wheelbase. It´s a poor mans Corse swingarm sorta/kinda.

//amullo
 

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Discussion Starter #10 (Edited)
The deal with the 30mm off set triples is it is supposed to increase trail.
This has been discussed to the point of nausea on another site with pictures and dotted lines so please don't start here, they really do increase trail. I noticed the increased force required to turn the 1098 before the switch to the 30 mm triples, it does feel like it is less but it is still there, much more so than the 600. Not that big of a deal really, I just have to shove on the bars more. I could, next time I have a serious break with reality, cough up the money for two sets of BST carbon fiber wheels.
Oh, I almost forgot!! I mounted a set of Dan Kyle's adjustable bars on the 1098, I call them "Roto Bars" that are a bit longer than stock giving a bit more leverage.
 

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I've got a 999S I hope to start playing with soon. I can't afford the track conversion parts yet.

The GSXR is a great handling bike.

The steering damper can alter the steering feel a lot. Rotating mass of the wheels will have more effect at high speed, little at lower speeds. Shorter (or less) offset of the triple clamp increases trail making the force that tends to straighten out the steering more. The trail is likely the # 1 contributing factor to steering feel.

The C.G. of the bike has a quite noticeable effect also. A higher C.G. and even a more centralized C.G. will make the bike turn more easily. I really don't know but I would guess that the GSXR is very good in regard to a compact and centralized C.G. because of the engine and transmission layout.

I wonder about the rotating mass? In general, the inline 4 is likely turning more RPM but is the rotating mass lighter? This will have an effect on the steering and turning performance.

Ducati riders are much more manly so we just push the bars harder :)
 
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